Transfer Case - High Shift Effort When Shifting

91chevy06

Number: 91-165-7A


Section: 7A


Date: January 1991


Corporate Bulletin No.: 967402R


Subject: HIGH TRANSFER CASE SHIFT EFFORT


Model and Year: 1983-91 T1 TRUCKS 1988-91 K TRUCKS


TO: ALL CHEVROLET DEALERS


THIS BULLETIN CANCELS AND SUPERSEDES DEALER SERVICE BULLETIN NO. 91-128-7A, DATED NOVEMBER 1990. THE BULLETIN NUMBER HAS BEEN CORRECTED IN THE FIRST PARAGRAPH. ALL COPIES OF 91-128-7A SHOULD BE DISCARDED.


Some four wheel drive K and T trucks may experience high transfer case shift effort and/ or total blockouts when "SHIFTING ON THE FLY" from 2H to 4H under cold weather conditions (usually 25 degrees or less). In order to shift to 4H the speed of the front propshaft must be increased to allow proper engagement of front axles. As the transfer case shift lever is moved into 4H the front propshaft begins rotating to synchronize the front axle assembly. In cold weather conditions regular production lube has high viscosity which may delay or prohibit the synchronizing of the front propshaft and axle resulting in high transfer case shift effort.


To reduce high shift effort, regular production front axle gear lube may be replaced with a 75W-90 synthetic gear lube which maintains a lower viscosity under cold weather conditions. This synthetic gear lube is now available in one quart containers from GMSPO. Before installing, it is important to drain and flush the front axle with clean mineral based (non synthetic) axle lube. The front axle should then be refilled to the level of the filler hole with synthetic lube listed below.

Front Axle Lube Capacities:

K1, K2 - 1.66 liter (1.75 qts)

K3 - 2.13 Liter (2.2 qts)

T1 - 1.20 liter (1.3 qts)


SERVICE PARTS INFORMATION

P/N DESCRIPTION

12345836 SAE 75W-90 synthetic gear lube, 1 qt. bottle
Parts are currently available from GMSPO.


WARRANTY INFORMATION For vehicles repaired under warranty use:


Labor Operation Number: T7980


Labor Time: .4 hr


Trouble Code: 92


NOTE: Labor Operation is coded to base vehicle coverage in the warranty system.